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Calculating pH for Polyprotic Acids and Buffers

I’m trying to understand how to calculate pH for polyprotic acids in different scenarios, especially in relation to buffers, and I have a couple of questions: When pH≫pKa or pH≪pKa, should I calculate ...
miiky123's user avatar
3 votes
0 answers
28 views

Non-binding buffer at pKa of roughly 6 that dissolves in ethanol?

I'm trying to find a proper buffer for my experiment, which I'd appreciate some suggestions on. I have a solution in which I want to measure the concentration of magnesium ions using a fluorescent ...
Helena's user avatar
  • 31
3 votes
0 answers
64 views

Assessing stability of protein used for interaction experiments after changing buffer from tris to HEPES

I have a protein with a theoretical $\mathrm{pI}~9.0$ currently stored in $\pu{25 mM}$ tris and $\pu{250 mM}$ $\ce{NaCl}$ $(\mathrm{pH}~8)$ at $\pu{−80 °C}.$ I need to do experiments in HEPES at $\...
TheChemist's user avatar
-2 votes
1 answer
107 views

Calculate the pH of a buffered solution after adding strong acid [closed]

Calculate the pH of a solution formed by the addition of $0.0020$ moles of $\ce{HCl}$ to $\pu{100.0 mL}$ of $\pu{0.200 M}$ $\ce{CH3NH2}$/ $\ce{0.100 M CH3NH3Cl}$. $K_\mathrm{b}(\ce{CH3NH2})=4.4\times ...
Shoes's user avatar
  • 33
-1 votes
1 answer
162 views

pH and degree of dissociation of drugs

I have a doubt, i hope not so stupid. Suppose we consider a buffer solution of acetic acid/acetate at pH = pKa = 4.76 and we add aspirin (pKa = 3.5): given that the pH of the solution is higher than ...
Luckenberg's user avatar
3 votes
0 answers
86 views

Measuring [A-]/[HA-] with Buffer and Indicator

I'm very confused on how to calculate the [A-]/[HA] value, given the fact that my dilution series uses buffers at various pH values with the same indicator (supplied at the same concentration to each ...
Tyler Anderson's user avatar
0 votes
1 answer
76 views

Why doesn't the volume of NH3 = 325 ml in this problem? [closed]

I'm struggling with the problem below, and don't understand why A buffer solution with pH = 9.0 is to be prepared from a 0.2 M ammonia solution and a 0.15 M $\ce{HCl}$ solution. The sum of the molar ...
wengen's user avatar
  • 423
0 votes
0 answers
40 views

Calculating acid volumes needed

I collect water quality samples used for irrigation. The samples are sent to a lab to measure $\ce{Ca^{2+}, Mg^{2+}, CO3^{2-}, HCO3^-}$, pH, and total dissolved solids. I need to use acid to prevent ...
sdabach's user avatar
  • 21
0 votes
1 answer
1k views

A method to create NH3-NH4Cl buffer solution using titration method

My aim is to create a basic buffer solution. I know that to create a basic buffer solution, we need a strong acid and weak base. In my case I have chosen $\ce{NH3}$ and $\ce{NH4Cl}$. Using titration, ...
Partth Kulkarni's user avatar
-3 votes
1 answer
83 views

pH calculation of a mixure containing 2 strong acids and a buffer mixture

Calculate the pH of a mixtureof 10 mL 0,1 M HCl ; 5 mL 0,1 M HNO3 ; 10 mL 0,2 M HAc ; 15 mL 0,4 M NaAc. My understanding was that I have to find the [H+] by: finding the concentration of the products ...
Jessica's user avatar
  • 11
0 votes
0 answers
66 views

How to find pH for acetate buffer?

Calculate the pH of the solution that results when $\pu{40.0 mL}$ of $\pu{0.100 M}$ $\ce{CH3COOH}$ is mixed with $\pu{30.0 mL}$ of $\pu{0.200 M}$ $\ce{NaCH3COO}.$ $K_\mathrm{a}(\ce{CH3COOH}) = \pu{1....
Nori's user avatar
  • 27
0 votes
0 answers
77 views

Finding dissolved amount of base from pH and solubility product

Calculate the amount of $\ce{Mg(OH)2}$ which is solubilized in $\pu{1.25 L}$ of a buffered solution at $\mathrm{pH} = 9.5$. $(K_\mathrm{sp}(\ce{Mg(OH)2}) = \pu{5.61E-12})$. From $\mathrm{pH}$ I ...
Rick88's user avatar
  • 109
1 vote
0 answers
58 views

Can addition of a "neutral" salt like NaCl assist pH test strip measurement accuracy in low ionic strength/poorly buffered solutions?

After a web-search, it seems ISAs (Ionic Strength Adjusters) are offered commercially to assist pH electrode/probe measurements. Presumably meant to increase conductivity (without affecting pH ...
revans19's user avatar
  • 129
0 votes
0 answers
146 views

How to estimate the pH of multi-component buffer (phosphate buffer in equilibrium with CO2 rich atmosphere)?

I wonder how the pH of buffer solution can be estimated if buffer consists of several systems in equilibrium to the gas phase. For example, (based on growth medium for one of the bacteria) buffer ...
Araneus0390's user avatar
0 votes
1 answer
852 views

pH of PBS after adding acetic acid

Why is there a need for pH adjustment below ? Can pH go below 4.3 after adding acetic acid to PBS ? “First prepare stock solution consisting of 50 ml of 10× PBS (pH 7.4), 12.5 ml of 80% glycerol, and ...
mete's user avatar
  • 103
-1 votes
1 answer
804 views

Prepairing a Sodium Acetate buffer - Meaning of molarity

We have instructions to prepare a "50 mM Sodium Acetate, pH 5 solution". I am not entirely sure what does the molarity refer to in this case. Does it mean: Add Sodium Acetate salt up to 50 ...
Keine's user avatar
  • 119
1 vote
0 answers
98 views

How do two species from the same buffer system have different pKa values? [closed]

$$ \begin{array}{lr} \hline \text{Reagent}~(\pu{0.1 M}~\text{solutions}) & \mathrm{p}K_\mathrm{a} \\ \hline \text{Ammonia} & 9.25 \\ \text{Acetic acid} & 4.75 \\ \text{Ammonium chloride} &...
Sincaia's user avatar
  • 19
1 vote
0 answers
59 views

Buffer problem in polyprotic acids [duplicate]

I read a problem which was as follows: Equal volumes of $\pu{1M} \ \ce{H3PO4}$ and $\pu{1M} \ \ce{Na3PO4}$ are mixed. The $\mathrm{pH}$ of the resultant mixture is (along with this $K_\mathrm{a1}, K_\...
Ashish's user avatar
  • 1,419
0 votes
2 answers
835 views

Calculating the pH of a 'buffer' solution?

Question: Determine the $\mathrm{pH}$ of the solution resulting when $\pu{100 cm^3}$ of $\pu{0.50 mol dm-3}$ $\ce{CH2ClCOOH}$ is mixed with $\pu{200 cm^3}$ of $\pu{0.10 mol dm-3}$ $\ce{NaOH}$. The ...
vgupt's user avatar
  • 153
-1 votes
1 answer
541 views

How to calculate how much weak acid would dissociate in water?

So I know water has a pH of 7. If we add 0.1 mol of a strong acid inside 1 liter of water, it WILL fully dissociate into 0.1 mol of A- and 0.1 mol of H+ thus making the pH of the solution 1. But what ...
Bruno Machado's user avatar
-4 votes
1 answer
793 views

How to calculate pH of an CH3COOH solution? [closed]

please, does anyone know, how to properly (with calculation procedure) calcutate $\mathrm{pH}$ of an $\ce{CH3COOH}$, when you know only: -$\ce{CH3COOH}$ is 8% (water solution) -density of $\ce{...
HASHTAG's user avatar
  • 11
5 votes
0 answers
190 views

What pH value of 1M sodium crotonate solution supposed to be?

I need to prepare the $\pu{1M}$ solution of sodium crotonate, however, I don't have one in lab, but I do have sodium hydroxide and crotonic acid. Thus, I calculated that for $\pu{100 mL}$ of $\pu{1M}$ ...
Araneus0390's user avatar
-2 votes
1 answer
2k views

How to change pH of CuSO4?

I'm currently very desperate to know this. I'm doing an experiment about adsorption/chelation of Cu ions in CuSO4 using banana peels using the UV-Visible spectroscopy. How do I change the pH of 0.1M ...
prata's user avatar
  • 134
-2 votes
2 answers
573 views

Why is sodium bicarbonate added to lower the pH? [closed]

I use salicylaldehyde, chloroacetic acid and sodium hydroxide for the synthesis of o-formylphenoxyacetic acid. In the procedure it is written that after the reaction I need to add sodium bicarbonate ...
Violet's user avatar
  • 138
-1 votes
1 answer
281 views

When is a buffer solution considered efficient?

By this I mean what is the rigorous definition of a buffer solution? I know that a buffer is a solution able to resist changes of $\mathrm{pH}$, but how much resistance to $\mathrm{pH}$ does a ...
lohe's user avatar
  • 27
0 votes
2 answers
19k views

Calculating ratio of conjugate base and acid when pH and pKa are given

Buffer solutions are used by biological mammalian systems to maintain the $\mathrm{pH}$ of blood plasma within a narrow range. In these systems, the compound from which this solution is obtained is $\...
Liz's user avatar
  • 1
2 votes
1 answer
300 views

Finding new pH after adding potassium hydroxide to citrate buffer

Calculate the $\mathrm{pH}$ change of citrate buffer containing $\pu{10.26 mmol}$ of citric acid and $\pu{6.98 mmol}$ citrate caused by adding $\pu{4.72 mmol}$ of potassium hydroxide. $\mathrm{p}K_\...
Dima's user avatar
  • 21
1 vote
1 answer
13k views

How to calculate bicarbonate and carbonate from total alkalinity [closed]

It's been a long time since I did my chemistry classes and I'm currently trying to analyze groundwater samples for hydrogeology purposes. I would like to evaluate carbonate and bicarbonate ...
Rachel's user avatar
  • 51
-1 votes
2 answers
440 views

Creating a buffer with with a target pH and given weak base?

I need to create a $100\textrm{mL}$ buffer of $\textrm{pH = 9.20}$ with ammonia and ammonium chloride such that $\textrm{pH = }9.20\pm0.50$ with $20\textrm{mL}$ of $0.2\textrm{M } \ce{NaOH}/\ce{HCl}$. ...
Andrew Li's user avatar
  • 155
0 votes
0 answers
52 views

Is contribution to pH by an acid or base always greater than salt hydrolysis?

I was solving a titration question and the reaction I came to was this: $$ \begin{array}{lcccc} \ce{&BOH(aq) &+ &HCl(aq) -> &BC(aq) &+ &H2O(l) }\\ \text{Initial} & x &...
naruto_022's user avatar
2 votes
2 answers
2k views

Can I make a buffer with a weak acid without adding it's conjugated base, when the desired pH of the solution is exactly the pKa of the weak acid?

An acid will be 50% dissociated when the solution it's in have a pH equal to the acid pKa ('afirmation 1', for later reference). We also know that a good buffer solution have equal concentrations of ...
d.J's user avatar
  • 21
8 votes
3 answers
4k views

Solubility Product and Buffers

The ionization constant of benzoic acid is $6.46 \times 10^{-5}$ and solubility product for silver benzoate is $2.5 \times 10^{-13}$. How many times silver benzoate is more soluble in a buffer of $\...
user avatar
2 votes
1 answer
5k views

How many moles NH4Cl must be added to NH3 to create buffer with pH=9?

How many moles of $\ce{NH4Cl}$ must be added to $\pu{2.0 L}$ of $\pu{0.10 M}$ $\ce{NH3}$ to form a buffer with $\mathrm{pH}=9$? Assume the addition does not change the volume of the solution ...
math_lover's user avatar
  • 1,398